<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>后盾人</title>
    <style>
        body {
            padding: 50px;
        }

        .field {
            position: relative;
            margin-bottom: 10px;
        }

        input {
            border: none;
            outline: none;
            width: 100%;
            text-align: center;
            color: #555;
        }

        .field::after {
            content: "";
            background: linear-gradient(to right, white, red, green, blue, white);
            display: block;
            height: 1px;
        }

        .field:hover::before {
            content: attr(data-help);
            color: #666;
            font-size: 12px;
            position: absolute;
            top: -10px;
            text-align: center;
            width: 100%;
        }
    </style>
</head>

<body>
    <div class="field" data-help="请输入100以内的字符">
        <input type="text">
    </div>
    <div class="field" data-help="请输入100以内的字符">
        <input type="text">
    </div>
    <div class="field" data-help="请输入100以内的字符">
        <input type="text">
    </div>
</body>

</html>